Present cable television systems utilize an r.f. transmission line with a plurality of amplifiers which are provided spaced apart along and in series with the line to feed distribution amplifiers and to maintain useable levels of signal along the line by compensating for transmission losses. Generally, the loss of amplification at any location will interdict the signal downline therefrom. The combination of the transmission line and amplifiers shall be termed a transmission line trunk. These amplifiers are configured to receive power from the line which is impressed upon the line by a plurality of spaced apart A.C. power sources coupled thereto. Each source is associated with the amplifiers of a different segment of the line or trunk, and filter means, such as stop-powered amplifiers, are located at the junctions between adjoining segments to prevent power flow therebetween. Consequently, in the event of loss of power at any particular power source and associated segment, all locations on that segment and downline therefrom are without useable signal resulting in considerable inconvenience to the cable t.v. subscribers until the power source is repaired.